Homopolymers and copolymers of unsaturated carboxylic acids are useful thickening agents. Such polymers can be cross-linked with a small amount of a known cross-linking agent for efficient thickening. One class of such polymers are prepared by polymerization of the acid in the presence of a free radical catalyst in mineral spirits forming a mineral spirits dispersion of the polymer.
The carboxylic acid polymers dispersed in mineral spirits have many applications such as in print-pastes and construction adhesives, however, upon storage or transportation in a container over long distances, the dispersed polymer tends to settle to the lower portion of the container and is often very difficult to redisperse. Mineral spirit dispersions of such polymers that are readily redispersible by shaking or simple stirring, even after long periods of storage or transportation over long distances, are desired.
The patent application of K. E. Burnfield, entitled "Stabilization of Mineral Spirit Dispersions of Carboxyl-Containing Polymers", filed Oct. 24, 1983 and bearing Ser. No. 544342, now abandoned, discloses stabilization of the carboxyl containing polymers in mineral spirits by the addition of a glyceryl tris-12-hydroxystearate and/or mixed saturated C.sub.18-36 fatty acid triglycerides. Such dispersions were thought to be stable, however, it was discovered that when these dispersions were transported in 55-gallon drums, the solids settled as a hard cake that was very difficult to redisperse.
Another patent application in this area is one entitled "Stable Mineral Spirit Dispersions of Carboxyl-Containing Polymers" filed Jul. 9, 1984 and bearing Ser. No. 629,040 now U.S. Pat. No. 4,536,528. This application discloses mineral spirit dispersions of carboxylic acid polymers which are rendered more stable by addition thereto of a block copolymer of propylene oxide and ethylene oxide, and glyceryl tris-12-hydroxystearate and/or mixed saturated C.sub.18-36 fatty acid triglycerides. The block copolymers are of propylene oxide and ethylene oxide having molecular weight of in the range of about 1,000 to 20,000 and containing about 10 to 80% by weight of polyoxyethylene units. Inventors in that application are Messrs. George and Lochhead.